1. Field
Non-limiting example embodiments relate to a thin film transistor (“TFT”), a method of manufacturing the same, and an organic light emitting diode (“OLED”) display device including the same. More particularly, non-limiting example embodiments relate to a TFT, which can prevent generated Joule heating from generating an arc during a conventional crystallization process.
2. Related Art
Annealing methods used during a crystallization process generally include a furnace annealing method using a heat treatment furnace, a rapid thermal annealing (“RTA”) method using radiant heat, e.g., a halogen lamp, etc., a laser annealing method using a laser, an annealing method using Joule heating, and so on. Among available annealing methods, an appropriate annealing method for the crystallization process is determined based on characteristics of material and process contemplated. Some of the factors to be considered in the selection of an appropriate annealing method are a range of an annealing temperature, uniformity of the annealing temperature, a heating rate, a cooling rate, purchase price, and maintenance cost. A selection of annealing method, however, becomes very limited when high temperature annealing or high rate annealing only in a local region of a material is needed.
While the laser annealing can rapidly anneal a surface of a material, the laser annealing method has only limited applicability since the applicability of the heat treatment is determined by a wavelength of a laser and the kind of materials requiring the heat treatment. In particular, when scanned linear laser beams overlap to anneal a large-sized device, non-uniformity in intensity of the laser beam and in irradiation level of the laser beam may occur. In addition, the laser annealing method requires expensive equipment, and thus, increasing maintenance cost.
The RTA method is widely applied to a semiconductor manufacturing process. With current technology, however, RTA method can be applied only to a silicon wafer having a diameter of 300 mm or less. The RTA method cannot be applied to a silicon wafer having a diameter larger than 300 mm because RTA method cannot uniformly anneal the silicon wafer having a diameter larger than 300 mm. Further, since a maximum heating rate of the heat treatment is 400° C./sec, it is hard to use the RTA method in a process requiring a higher heating rate than 400° C./sec.
Therefore, researches have been widely conducted on annealing methods to solve these problems and to eliminate processing limitations.